package text;
import java.util.Scanner;
public class text {
	public static void main(String[] args)
	{	
    	Scanner in = new Scanner(System.in);
	    // get first input
	    //System.out.print("n");
	    //String a = in.nextLine();
	    //for(int i=0;i<a.length();i++)
	    //{ 
	    	//int n = Integer.parseInt ([String]);
	    	
	    //}
    			while (true) 
    			{	
    				float n=in.nextFloat();
    				double m=0.0000;
    				if(n<0) System.out.print(Double.NaN+"\n");
    				else 
    					if(n==0)System.out.print("0.000000"+"\n");
	    				else
	    				{	
		    				while(true)
		    				{  
								m+=0.0001;	
								if(n-(Math.pow(m, 2))<0.0001||(Math.pow(m, 2))>=n)break;
							}	
		    				System.out.printf("%.6f\n",m);
		    					}					
		    				}		
    	    }}
	   


